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Fix R_AVR_7_PCREL and R_AVR_13_PCREL range checking #92695

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Merged
merged 2 commits into from
May 23, 2024
Merged

Fix R_AVR_7_PCREL and R_AVR_13_PCREL range checking #92695

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b60ee41
[lld][AVR] Fix range of R_AVR_7_PCREL
aykevl May 19, 2024
7a64998
[lld][AVR] Allow R_AVR_13_PCREL to overflow
aykevl May 19, 2024
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3 changes: 1 addition & 2 deletions lld/ELF/Arch/AVR.cpp
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Expand Up @@ -231,14 +231,13 @@ void AVR::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {

// Since every jump destination is word aligned we gain an extra bit
case R_AVR_7_PCREL: {
checkInt(loc, val - 2, 7, rel);
checkInt(loc, val - 2, 8, rel);
checkAlignment(loc, val, 2, rel);
const uint16_t target = (val - 2) >> 1;
write16le(loc, (read16le(loc) & 0xfc07) | ((target & 0x7f) << 3));
break;
}
case R_AVR_13_PCREL: {
checkInt(loc, val - 2, 13, rel);
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I did not catch your point at here, indeed RJMP/RCALL have a range limit of [-4096, 4094], why we can not check it for attiny85 ? And How can it jump over 4KB with RJMP on attiny85?

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Is there an example, that RJMP can exceeds 4094 bytes on attiny85, which is allowed by avr-ld ?

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Looks like these were older comments?

checkAlignment(loc, val, 2, rel);
const uint16_t target = (val - 2) >> 1;
write16le(loc, (read16le(loc) & 0xf000) | (target & 0xfff));
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5 changes: 2 additions & 3 deletions lld/test/ELF/avr-reloc-error.s
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Expand Up @@ -3,7 +3,7 @@
# RUN: rm -rf %t && split-file %s %t && cd %t

# RUN: llvm-mc -filetype=obj -triple=avr -mcpu=atmega328 avr-pcrel-7.s -o avr-pcrel-7.o
# RUN: not ld.lld avr-pcrel-7.o -o /dev/null -Ttext=0x1000 --defsym=callee0=0x1040 --defsym=callee1=0x1044 --defsym=callee2=0x100f 2>&1 | \
# RUN: not ld.lld avr-pcrel-7.o -o /dev/null -Ttext=0x1000 --defsym=callee0=0x1040 --defsym=callee1=0x1084 --defsym=callee2=0x100f 2>&1 | \
# RUN: FileCheck %s --check-prefix=PCREL7
# RUN: llvm-mc -filetype=obj -triple=avr -mcpu=atmega328 avr-pcrel-13.s -o avr-pcrel-13.o
# RUN: not ld.lld avr-pcrel-13.o -o /dev/null -Ttext=0x1000 --defsym=callee0=0x2000 --defsym=callee1=0x2004 --defsym=callee2=0x100f 2>&1 | \
Expand All @@ -20,7 +20,7 @@
__start:

# PCREL7-NOT: callee0
# PCREL7: error: {{.*}} relocation R_AVR_7_PCREL out of range: {{.*}} is not in [-64, 63]; references 'callee1'
# PCREL7: error: {{.*}} relocation R_AVR_7_PCREL out of range: {{.*}} is not in [-128, 127]; references 'callee1'
# PCREL7: error: {{.*}} improper alignment for relocation R_AVR_7_PCREL: {{.*}} is not aligned to 2 bytes
brne callee0
breq callee1
Expand All @@ -34,7 +34,6 @@ brlt callee2
__start:

# PCREL13-NOT: callee0
# PCREL13: error: {{.*}} relocation R_AVR_13_PCREL out of range: {{.*}} is not in [-4096, 4095]; references 'callee1'
# PCREL13: error: {{.*}} improper alignment for relocation R_AVR_13_PCREL: {{.*}} is not aligned to 2 bytes
rjmp callee0
rcall callee1
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12 changes: 12 additions & 0 deletions lld/test/ELF/avr-reloc.s
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Expand Up @@ -82,13 +82,25 @@ sbic b, 1 ; R_AVR_PORT5
; CHECK-NEXT: rjmp .-36
; CHECK-NEXT: breq .+26
; CHECK-NEXT: breq .-40
; CHECK-NEXT: rjmp .-4096
; CHECK-NEXT: rjmp .+4094
; CHECK-NEXT: rjmp .+4094
; CHECK-NEXT: rjmp .-4096
; CHECK-NEXT: breq .-128
; CHECK-NEXT: breq .+126
; HEX-LABEL: section .PCREL:
; HEX-NEXT: 0fc0eecf 69f061f3
foo:
rjmp foo + 32 ; R_AVR_13_PCREL
rjmp foo - 32 ; R_AVR_13_PCREL
breq foo + 32 ; R_AVR_7_PCREL
breq foo - 32 ; R_AVR_7_PCREL
rjmp 1f - 4096 $ 1: ; R_AVR_13_PCREL
rjmp 1f + 4094 $ 1: ; R_AVR_13_PCREL
rjmp 1f - 4098 $ 1: ; R_AVR_13_PCREL (overflow)
rjmp 1f + 4096 $ 1: ; R_AVR_13_PCREL (overflow)
breq 1f - 128 $ 1: ; R_AVR_7_PCREL
breq 1f + 126 $ 1: ; R_AVR_7_PCREL
Comment on lines +98 to +103
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For those not familiar with this syntax, the $ symbol works as a newline.
So this code:

rjmp 1f - 4096  $ 1:

Is equivalent to the following:

rjmp 1f - 4096
1:

(where 1f refers to the next anonymous label numbered "1")


.section .LDSSTS,"ax",@progbits
; CHECK-LABEL: section .LDSSTS:
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